THE EFFECT OF AGITATION ON PULLULAN PRODUCTION BY A WHITE MUTANT AUREOBASIDIUM PULLULANS B-1 IN BATCH CULTURE

摘要

In this study we indicated a way of producing pullulan using a new strainof ?Aureobasidium pullulans, the white mutant B-1. The fungus culturewas run in a stirred bioreactor. Five different impeller speeds were applied:200 rpm, 400 rpm, 600 rpm, 800 rpm, and 1000 rpm. The kinetics of changes inair saturation of medium, the content of pullulan, cell biomass, residual sugarand pH were investigated. The maximum concentrations of pullulan (26.2g×dm~(-3))and biomass (14.4 g d.w.×dm~(-3)), and the maximum saccharoseconsumption (>99%) were achieved in the culture stirred at 800 rpm after 96hof incubation. In this culture, air saturation (DO) has decreased to 45–50% within36h. That DO value was maintained until the end of fermentation. The pH valuehas decreased from an initial 6.5 to 5.35. Agitation speeds in the range of 200–600rpm and at 1000 rpm were not? so beneficial. The respective cultures were characterizedby both: ?lower biomass yield and lower pullulan content. The B-1 mutant culturewith adjusted pH, maintained at ?6.5, and agitation rate of 800 rpm was morebeneficial for biomass growth (18.5 g d.w.×dm~(-3)) than for pullulan production(16.2 g×dm~(-3)). The data demonstrated that agitation speed influenced pullulanbiosynthesis by A. pullulans B-1. Mutant B-1 is suggested as a potentialcandidate for industrial pullulan production.